Hydraulically driven working machine for die-casting, injection molding, and the like



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Patented Aug. 25, 1953 HYDRAULICALLY DRIVEN WORKING MA- CHINE FORDIE-CASTING, INJECTION MOLDING, AND THE LIKE Wilibald A. Venus, Munich,Germany, assignor to Hahn & Kolb, Stuttgart-N, Germany ApplicationSeptember 28, 1949, Serial No. 118,284 In Germany October 1, 1948 5Claims.

Die-casting machines preferably fed 'by using hand ladles have ingeneral hydraulically driven injection plungers. Thus the plunger has toper form a considerable idle stroke before it forces the filled-inmaterial into the die cavity. This occurs especially in thoseconstructions of machines where the materialtravels with the pistontouching its surface for a considerable part of the stroke, before it isforced into the die, no pressure being exerted on the material during apart of the stroke. With this kind of machines, that part of the workingstroke within which the material is forced into the die, is only a smallpart of the full stroke. Therefore, if the stroke is performed with fullpressure, a very high amount of pressure fluid willbe wasted inconsequence of the large idle portion of the stroke consuming the mainpart of the pressure fluid.

It has already been suggested to move the plunger during the idle strokeby applying pressure fluid of lower pressure and to change to highpressure when the plunger touches the casting material, the highresistance of said material being used for control. As, on the one hand,the movements are performed with high speed and, on the other hand, theinertia of the pressure fluid to be moved under high pressure isconsiderable and working speeds varying within a wide range arerequired, the full pressure could not become effective precisely at themoment desired.

This aforesaid method fails with all hydraulically operated machinesworking with a pressure fluid delivered by one pressure source. To avoidthis drawback it has been sugggested to move the plunger during its idlestroke by an auxiliary plunger. As soon as said auxiliary plungertouches the material, a resistance is built up serving to change thepressure supplied to the main plunger. For the reasons mentioned above,this method did not give satisfactory service, especially as during thewhole pressing stroke the maximum pressure was not available. Moreover,the released pressure became, due to the inertia of the control meansand of the pressure fluid,

effective too late if only released at the moment when the resistance inthe cylinder has reached a predetermined amount.

Furthermore, the main piston has been connected with the auxiliarypiston in such a way as to automatically transfer the pressure to themain piston as soon as the speed had become undesirably low. This, too,is not advantageous, for, as the speed decreases because of the materialbeginning to solidify in the sprue thus slacking the movement, thetransfer to the main piston is eiiected too late as to positivelycounteract the solidifying.

One object of the invention is to avoid this drawback and to provide animproved driving device for hydraulically operated machines such asdie-casting machines, press-casting machines, etc., comprising anauxiliary piston and a main piston, the latter immediately followingsaid auxiliary piston, and operating under the same fluid pressure assaid piston in such a manner that the auxiliary piston opens by its ownmovement the inlet channel for the pressure fluid to the main plunger,and that the main plunger now starting its working movementautomatically shuts off the pressure fluid having previously entered thecylinder of the auxiliary plunger, by increasing the pressure therein.

Another object of the invention is to provide the cylinder of theauxiliary plunger in the interior of the main plunger itself and tosupply both plungers with pressure fluid from a common pressure fluidconduit, one branch of which leading through a check valve to theauxiliary plunger and the other branch leading directly to the mainplunger, the cylinder of which being opened by the movement of theauxiliary plunger. Thus the continuallymoving pressure fluid is led,without any interruption, via a second branch to the working pistoninstead of through a branch meanwhile closed by a check valve. T'orelease the cylinder of the auxiliary plunger of the fluid pressuretherein, a controlled outlet valve which by-passes the check valve, isprovided in the emptying conduit leading to the outlet conduit.

Other objects and features of novelty to be hereinafter described willbe apparent from the following specification.

In the accompanying drawing which schematically shows an illustrativeembodiment of the present invention I is a main plunger in which anauxiliary plunger 2 is provided. 3 is an inlet valve from which pressurefluid conduit5 with branch I!) leads via check valve I through atelescopic tube 8 and bores 9 into cylinder space I2 of auxiliaryplunger 2. Another branch 2| of conduit leads into space 22, which issituated above hollow elongation 6 of auxiliary plunger 2 and is withsome clearance slidably guided in a bore of main cylinder I0.

As soon as by a clockwise movement of lever valve 3 has been opened anda second or outlet valve 4 has been closed, pressure fluid will enterthrough conduit 5 via branch I9 and bore 9 into cylinder space I2 aboveauxiliary piston 2. Inside cylinder space I2 pressure will build upwhich forces main piston I upward against the bottom of main cylinder I0and shifts auxiliary piston 2 connected with piston head I3 downwarduntil said auxiliary piston 2 will be stopped by abutment I4 of mainpiston I. This is the case when piston head I3 has traveled distance itand reached the surface of the molten casting or injection material I6filled into filling and compression chamber I'I.

Preferably, elongation 6 of auxiliary plunger 2 as well as abutment Mwill be made adjustable (not represented in the drawing). The adjustmentis such that elongation 6 extending with some clearance into the bore ofcylinder It, leaves said bore shortly before the portion 71, of thestroke is completed. Thereby, the pressure fluid passing through conduit5 with full velocity, has free admission to cylinder space II of mainpiston I. The sudden and rapidly entering of the pressure fluid causesmain piston I to begin its downward or working movement with high speed.Momentarily it presses thereby with its full downward pressure upon thepressure fluid in cylinder space I2, thus increasing the pressure of thefluid which immediately (outlet valve 4 remaining closed) shuts offcheck valve I. By

means of said pressure fluid enclosed in space I2 and acting like asolid body, the piston head is now subjected to the full pressureexerted by fluid acting in space II or the upper effective area of mainpiston I via auxiliary piston 2, said piston head thus being able toperform its working stroke with high pressure, especially so because thestill moving pressure fiuid, hitherto traveling via check valve I toauxiliary piston 2, may now be supplied directly and momentarily toworking space II of main piston I via branch H and space 22.

After piston head I3 has finished its downward stroke and thus forcedthe material, preferably metal, into the die cavity, inlet valve 3 willbe closed by anticlockwise rotation of lever 21 and outlet valve 4 willbe opened. Therefore, under the effect of return piston I8 constantlybeing under pressure, pistons I and 2 will be lifted through rods I5into their upper extreme positions, whereby first the pressure fluidenclosed in cylinder space I2 of auxiliary piston 2 is displaced throughconduit I9 by-passing the back-pressure valve I, and then the pressurefluid of cylinder space II is displaced through the annular clearance 25which exists between the prolongation 6 of piston 2 and the upperportion of cylinder Ill, via space 22, conduit 2I and through valve I todischarge conduit 23.

According to the invention the advantage will be obtained that, byproviding auxiliary piston 2 in the interior of working or main piston Iand by arranging check valve I in a branch of the pressure fluidconduit, piston head I3 will perform its idle stroke with only a minimumforce exerted by the high pressure fluid. Thus it will be achieved thatauxiliary piston 2 itself will, at a predetermined intermediate positionof the stroke and quite independent from the pressure of the castingmaterial, automatically transmit the pressure fluid to Working or mainpiston I. Said piston will now perform the working part of the strokewith high pressing power and at an adjustable speed which may bedifferent from that of the idle stroke and can e. g. be adjusted bythrottling supply branch 2I.. If in the supply branch 2I .an adjustablethrottle 21 is provided it will be possible to regulate the flowingspeed of the fluid passing through supply branch 2I by adjusting thethrottle 21. By this means, the working speed of the plunger can beincreased or decreased respectively.

Independent from the example represented in the drawing, it also lieswithin the scope of the present invention to arrange the pressurecylinder of the main or working piston between the auxiliary piston andthe main piston, thus causing auxiliary piston, during its idle stroke,to move the main piston together with the working cylinder, whilst theworking movement proper of the stroke which forces the metal into thecavity of the die is performed by the continued movement of the workingpiston alone.

I claim:

1. In die-casting, injection molding and like hydraulically operatedworking machines comprising a hydraulic main cylinder, a main piston inthe cylinder, an auxiliary piston in the main piston, a cylinder for theauxiliary piston formed by and in the main piston, a pressure fluidsupply conduit common to both cylinders, a check valve having a movablevalve member, an inlet valve in said conduit, said conduit having twobranches, one of which connects by the check valve with the interior ofthe auxiliary cylinder and the other branch connects with the maincylinder, the movable valve member of said check valve closingautomatically when the pressure on its backside in the direction of theflow is at least approximately equal to the pressure on its front side,an outlet valve arranged on the back pressure side of said check valve,said main and auxiliary cylinders being arranged with respect to theirpistons that, under the influence of the pressure submitted from saidcommon supply conduit, the pistons will perform the working stroke ofsaid machine so that first the auxiliary piston begins moving and afterbeing stopped by an abutment of the main piston, the working stroke iscontinued by both pistons, control means to interrupt and respectivelyfully open the connection between the second-mentioned branch and themain cylinder, the movement of said auxiliary piston immediately beforecontacting the abutment causing the opening movement of said controlmeans so that the fluid through said second-mentioned branch may enterthe main cylinder and initiate the stroke of the main piston which, byincreasing the pressure in the auxiliary cylinder automatically closesthe check valve, thereby locking the pressure fluid within saidauxiliary cylinder for the further common travel of the working stroke.

2. In die-casting machines according to claim 1, in which said controlmeans is provided with a piston-like member movable in a hole andmovable out of the hole when the auxiliary piston contacts the abutment.

3. In die-casting machines according to claim 1, in which said controlmeans is provided with a piston-like member movable in a hole andmovable out of the hole when the auxiliary piston contacts the abutment,the piston-like member being firmly connected to the auxiliary piston.

4. In die-casting machines according to claim 1, in which said controlmeans is provided with a piston-like member movable in a hole andmovable out of the hole when the auxiliary piston contacts the abutment,the piston-like member and its hole having a clearance to allow thereturn flow of the residual pressure fluid out of the main cylinderafter the piston-like member has moved into the hole during the endportion of the return stroke.

5. In die-casting machines according to claim 5 ton contacts theabutment.

WILIBALD A. VENUS.

References Cited in the file of this patent UNITED STATES PATENTS 10Number Name Date 612,507 Rothe Oct. 18, 1890 2,351,872 Parker June 20,1944 2,453,785 Cousino NOV- 16, 1948

